This invention concerns improvements in and relating to winches, and more especially to winches of the kind that may be subject to wide fluctuations in load during operation of the winch drive.
In the case of a winch arrangement that is intended for the rapid shifting of wheeled vehicles of a kind that incorporate their own braking system which may be under the control of an occupant of the vehicle during winching thereof, the winch arrangement may become subject to wide variations in load due to a lack of coordination between the operation of the winch drive and the operation of the braking system of the vehicle. This problem is especially acute in the case of a winch to be applied to aircraft which may need to be hauled rapidly into a hanger or other enclosure, since the efficiency of the braking system of an aircraft is such that very substantial and sudden loads can be placed on the winch rope, causing possible damage to the aircraft and/or the winch itself. Moreover, there is a requirement that slackness in the winch rope must be prevented in the event that an aircraft should overrun the winch, for example due to failure to apply the aircraft brakes following stoppage of the winch motor, and therefore means, operating independently of the winch motor, must be provided for taking up slack in the rope in these circumstances. In practice this could be provided for by arranging that the inertia of the system is such that this can run on to drive the winch drum after cease of drive from the drive motor, in order to wind up slack rope. This relatively high inertia of the system, however, would only increase the problems associated with sudden overloading of the winch rope.